Electronically-controlled fuel injectors are designed to inject precise amounts of fuel into an engine combustion chamber for combustion to generate motive power. The fuel injectors are connected to a fuel tank and include internal fluid chambers, fluid passages, and control valves that communicate fuel through the injector between injection events. During an injection sequence, the control valves move in a predetermined timing sequence to open and close the various fluid passages and fluid chambers so that pressurized fuel is injected into the combustion chamber at the appropriate time from an injection tip of the injector.
In prior fuel injectors, control valves within the injector have been actuated by one or more solenoids that receive control signals from an electronic control. In response to the control signals, the solenoids are operable to cause the control valves to move from one position to another so that fuel is communicated through the injector and to the injector tip in a desired manner. Compression springs may be used to move the control valves to a return position when the control signals are terminated.
In such solenoid-controlled injectors, it is often difficult to accurately control movement and positioning of the control valves through the control signals applied to the solenoids. This is especially true when intermediate positioning of a solenoid-controlled valve between two opposite, fixed positions is desired. Solenoid-controlled valves, by their very nature, are susceptible to variability in their operation due to inductive delays, eddy currents, spring pre-loads, solenoid force characteristics and varying fluid flow forces. Each of these factors must be considered and accounted for in a solenoid-controlled fuel injector design. Moreover, the response time of solenoids limits the minimum possible dwell times between multiple injection events and makes the fuel injector generally more susceptible to various sources of variability.
The present invention is directed to one or more of the problems set forth above.